Recently, as a multimedia technology is developed, an electronic device having various functions has appeared. As these devices, for example, there is a portable terminal mainly classified into a smart phone. These devices generally have a convergence function of complexly performing one or more functions.
Particularly, a portable terminal, which is being recently launched, has a function capable of receiving airwave broadcasting (for example, terrestrial Digital Multimedia Broadcasting (DMB)) and playing back a music file or photographing and playing back a moving picture in high definition in addition to a basic calling function.
When performing these various supplementary functions, a portable terminal additionally uses an earphone device (generally, called an ‘earphone’) including an earplug inserted into an ear jack hole of an ear jack provided in a corresponding device. In this earphone device, an earplug is provided at one end of a cable of a predetermined length, and a pair of earphones for listening to sound in stereo is installed at the other end thereof. Also, generally, a microphone is installed in a middle of the cable to perform a hands free function upon call.
The aforementioned earplug generally uses a 3-pole or 4-pole terminal. Each terminal is installed in an electrical insulation state. If being connected to an ear jack, each terminal comes into contact with a corresponding pin installed in a corresponding location of the ear jack, whereby each terminal performs a corresponding function.
For example, in a 3.5 pie 3-pole terminal of an earplug, a first terminal of the lowest side, a 2nd terminal of the top thereof, and a 3rd terminal of the top thereof, which take charge of SPK_L, SPK_R, and GND, respectively, are electrically connected with corresponding pins of an ear jack and perform functions.
Also, in a 4-pole terminal of the earplug, a first terminal of the lowest side, a 2nd terminal of the top thereof, a 3rd terminal of the top thereof, and a 4th terminal of the top thereof are electrically connected with corresponding pins of the ear jack, which take charge of SPK_L, SPK_R, GND, and MIC, respectively, and perform functions.
An ear jack for housing an earplug as described above is of a construction of connecting corresponding terminals of the earplug correspondingly to a plurality of pins installed in different locations within one housing. This can cause a detection error problem in course of inserting the earplug into the ear jack.
For instance, a sense pin for sensing the insertion or non-insertion of the earplug is installed at a housing end of the ear jack. Although the earplug is not fully (i.e., loosely) inserted into the ear jack, if a SPK_L terminal of the earplug gets into contact with the sense pin, a portable terminal detects the insertion of an earphone. But in this case, because the earphone is inserted into the portable terminal, the portable terminal detects a low signal by the sense pin. Due to this, the portable terminal supplies a voltage to a MIC_Bias terminal in order to check the insertion or non-insertion of a microphone. But, because the MIC terminal has not been connected with a MIC pin of the ear jack, the voltage applied to the MIC_Bias terminal is floated and is again applied to the SPK_L terminal and the sense pin. Due to this, the sense pin receives a high signal applied and detects as the earplug is uninstalled. Accordingly, the portable terminal eliminates the voltage applied to the MIC_Bias terminal. Due to this, the sense pin again receives a low signal applied and detects as the earplug is again inserted.
That is, in a state where the earplug is not fully inserted into the ear jack but the SPK_L terminal comes into contact with the sense pin, the portable terminal repeatedly performs the aforementioned operation. During this process, a periodic noise of 8 Hertz (Hz) interval is generated. This not only has given a feeling of displeasure to a user but also has become the cause of erroneous operation.